# define _CRT_SECURE_NO_WARNINGS 1
# include <stdio.h>
int main()
{
	unsigned int num;
	scanf("%d", &num);
	if (num < 60)
	{
		printf("E\n");
	}
	else if (num < 70)
	{
		printf("D\n");
	}
	else if (num < 80)
	{
		printf("C\n");
	}
	else if (num < 90)
	{
		printf("B\n");
	}
	else
	{
		printf("A\n");
	}
	return 0;
}